Highly efficient isocyanate-free microwave-assisted synthesis of [6]-oligourea

Abdussalam K. Qaroush, Asmaa S. Al-Hamayda, Yasmeen K. Khashman, Sergei I. Vagin, Carsten Troll, Bernhard Rieger

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28 Scopus citations


A new eco-friendly, isocyanate-free, energy-saving method for the production of [6]-oligourea, utilizing a green carbonylating agent, viz. propylene carbonate, is reported. It comprises an organocatalyzed, microwave-assisted, solvent-free synthesis. Two modes of microwave-assisted synthesis, viz. dynamic and fixed energy modes, were applied. Upon optimization, the dynamic mode gave 79% yields of [6]-oligourea. On the other hand, almost quantitative yields were obtained using the fixed mode, within 20 min, at 10 W and with the same catalyst loading. Combination of both organocatalysis and microwave energy input appears to be a key issue for the efficiency of the reaction, with the fixed energy mode being best suited. It should be noted that all data reported are reproducible (due to the homogeneous microwave technology used by CEM Discover S-Class of microwave reactors). To the best of our knowledge, this is the best eco-friendly synthetic approach for the preparation of the title oligomers. It paves the way for using more of the biorenewable and sustainable chemicals as a feedstock for the production of polyureas. The oligomer produced was analyzed by EA, ATR-FTIR, XRD, 1H and 13CNMR. Furthermore, thermal properties of the resulting [6]-oligourea were analyzed using TGA and DSC. © The Royal Society of Chemistry 2013.
Original languageEnglish (US)
Pages (from-to)2221
JournalCatalysis Science & Technology
Issue number9
StatePublished - 2013
Externally publishedYes

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): UK-C0020/KSA-C0069
Acknowledgements: A. K. Q. is grateful to King Abdullah University for Science and Technology, KAUST for the financial support of the scholarship of his PhD for the project UK-C0020/KSA-C0069. In addition, we thank Dr Wolfgang Eisenreich and Dr Timo Anselment for their help with the NMR experiments.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.


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